So the idea of a coprocessor is that it can handle the button pressed, take over the screen during boot up (I really hate that ugly boot screen with all the text). I want to show a class nintendo screen as well as play a sound file. A simple 8-bit SPI DAC will be used to connect to the speaker. After a certain amount of time, a bus switch will be used to turn on the output of the Raspberry PI to the screen. The coprocessor is a ATMEGA32U2 which has a built in USB host, which makes it very easy to emulate a USB device.